This invention relates to a heat exchanger used as an inter-cooler in a rotary compressor machine such as a turbocharger or a super-charger for engines.
Combustion air chargers, such as turbochargers or super-chargers, have been employed with engines, particularly internal combustion engines, for many years. In a turbocharger, at least one rotary compressor wheel is driven by the exhaust of the engine. In the case of a supercharger, at least one rotary compressor wheel is driven mechanically, usually by the rotary output of the engine. In either case, a compressor wheel is employed to compress ambient air prior to its admission to the engine to support combustion therein. Because the air is compressed, a given volume thereof will have a greater mole content of oxygen than an otherwise equal of volume of air at ambient pressure. As a consequence, the additional oxygen permits the combustion of a greater quantity of fuel so that for a power plant of a given size, a greater power output may be derived as a result of the charging of the combustion air.
Over the years, it has been determined that the efficiency of such combustion air charging devices can be improved through the use of a so-called intercooling system. Because the air is heated as it is compressed, part of the efficiency derived by employing the combustion air charging device in the first place, i.e., the densification of the combustion air charged to the engine, is lost because a volume of hot compressed air will contain less oxygen than an equal volume of cooler compressed air when both are at the same pressure. Thus, for a given pressure, upon admission to an engine for combustion, a cooler combustion air charge will allow the development of more power within the engine than the same charge at the same pressure if at a higher temperature.
Consequently, intercoolers as mentioned previously have been employed to cool the air after it exits the combustion air charger (or a stage thereof) and prior to its admission to the engine so as to provide, for any given pressure, a maximum mole content of oxygen.
In many cases, the intercooler will be employed as a conventional, rectangular-shaped heat exchanger and is mounted side-by-side or to the front or rear of the usual heat exchanger employed for cooling engine coolant. While this sort of an arrangement adequately handles the cooling of the pressurized combustion air, it may have certain constraints in terms of size and the volume available in an engine compartment as, for example, in a vehicle, that houses both the engine and the various heat exchangers employed for cooling. It also may require extensive hose connections between the turbocharger, the intercooler and the engine combustion air inlet which necessarily require relatively large diameter hoses because of the low density of the combustion air and the consequent large volume thereof.
It has therefore been proposed to incorporate the intercooler within the combustion air charger itself to provide a more compact combustion air charging and intercooling system as well as to avoid large, bulky hose connections to the extent possible. The goal here is to incorporate the intercooling heat exchanger within the combustion air charger in such a way that it may be easily serviced, requires a minimum of plumbing connections and does not unduly increase the bulk of the combustion air charger while at the same time maximizing the cooling of the combustion air after compression thereof.
The present invention is directed toward the provision of advantageous solutions to these problems in an intercooling heat exchanger that is intended to be located internally within a rotary compressor machine.
It is the principal object of the invention to provide a new and improved rotary compressor machine with intercooling for use in cooled, compressed air. More specifically, it is the object of the invention to provide an improved rotary compressor machine with an internal inter-cooler that is more compact than known such systems, that is easily serviced, and/or which requires a minimum of plumbing connections and which maximizes the efficiency of the air cooling process.
According to one facet of the invention, an exemplary embodiment thereof achieves one or more of the above objects in a rotary machine that includes a rotatable shaft having at least one compressor wheel thereon and a housing containing the compressor wheel and having an inlet to the compressor wheel and an outlet. A heat exchanger is disposed in the housing and is located between the compressor wheel and the outlet. The heat exchanger includes a core having a gas flow path with a substantial radial extent and a gas inlet in fluid communication with the compressor wheel and a gas outlet in fluid communication with the housing outlet. A coolant flow path is provided in the heat exchanger in heat exchange relation with the gas flow path and has a substantial axial extent. The heat exchanger has a donut-shaped core containing the flow paths, the core being substantially concentric with the shaft. The core is flanked by axially spaced, donut-shaped tanks with one such tank serving as a boundary for compressed air being discharged by the compressor wheel as it moves in a radially outward direction. The invention contemplates that the tank be thermally conductive and that the usual deswirling vanes mounted in this area near the outlet of the compressor wheel be thermally bridged to such tank so that, in addition to providing the usual deswirling function, the vanes further act as fins to which heat of the compressed air may be rejected to ultimately be conducted through the tank to coolant therein to thereby increase the transfer of heat from the compressed gas to the coolant.
In a preferred embodiment, the vanes are part of a metallic vane structure which is metallurgically bonded to the tank.
In a highly preferred embodiment, the rotary machine is a turbocharger or a supercharger and the heat exchanger serves as an inter-cooler for combustion air.
In one embodiment of the invention, the vane structure comprises a plurality of circumferentially spaced vanes bonded to the tank.
The invention contemplates that the heat exchanger has a radially outer periphery spaced inwardly of the housing and the core has a gas inlet at the radially outer periphery to receive the discharged gas after the same has passed through the vane structure.